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Diffstat (limited to 'tools/binman/cbfs_util.py')
| -rw-r--r-- | tools/binman/cbfs_util.py | 887 |
1 files changed, 887 insertions, 0 deletions
diff --git a/tools/binman/cbfs_util.py b/tools/binman/cbfs_util.py new file mode 100644 index 00000000000..45e16da0aaa --- /dev/null +++ b/tools/binman/cbfs_util.py @@ -0,0 +1,887 @@ +# SPDX-License-Identifier: GPL-2.0+ +# Copyright 2019 Google LLC +# Written by Simon Glass <sjg@chromium.org> + +"""Support for coreboot's CBFS format + +CBFS supports a header followed by a number of files, generally targeted at SPI +flash. + +The format is somewhat defined by documentation in the coreboot tree although +it is necessary to rely on the C structures and source code (mostly cbfstool) +to fully understand it. + +Currently supported: raw and stage types with compression, padding empty areas + with empty files, fixed-offset files +""" + +from __future__ import print_function + +from collections import OrderedDict +import io +import struct +import sys + +import command +import elf +import tools + +# Set to True to enable printing output while working +DEBUG = False + +# Set to True to enable output from running cbfstool for debugging +VERBOSE = False + +# The master header, at the start of the CBFS +HEADER_FORMAT = '>IIIIIIII' +HEADER_LEN = 0x20 +HEADER_MAGIC = 0x4f524243 +HEADER_VERSION1 = 0x31313131 +HEADER_VERSION2 = 0x31313132 + +# The file header, at the start of each file in the CBFS +FILE_HEADER_FORMAT = b'>8sIIII' +FILE_HEADER_LEN = 0x18 +FILE_MAGIC = b'LARCHIVE' +FILENAME_ALIGN = 16 # Filename lengths are aligned to this + +# A stage header containing information about 'stage' files +# Yes this is correct: this header is in litte-endian format +STAGE_FORMAT = '<IQQII' +STAGE_LEN = 0x1c + +# An attribute describring the compression used in a file +ATTR_COMPRESSION_FORMAT = '>IIII' +ATTR_COMPRESSION_LEN = 0x10 + +# Attribute tags +# Depending on how the header was initialised, it may be backed with 0x00 or +# 0xff. Support both. +FILE_ATTR_TAG_UNUSED = 0 +FILE_ATTR_TAG_UNUSED2 = 0xffffffff +FILE_ATTR_TAG_COMPRESSION = 0x42435a4c +FILE_ATTR_TAG_HASH = 0x68736148 +FILE_ATTR_TAG_POSITION = 0x42435350 # PSCB +FILE_ATTR_TAG_ALIGNMENT = 0x42434c41 # ALCB +FILE_ATTR_TAG_PADDING = 0x47444150 # PDNG + +# This is 'the size of bootblock reserved in firmware image (cbfs.txt)' +# Not much more info is available, but we set it to 4, due to this comment in +# cbfstool.c: +# This causes 4 bytes to be left out at the end of the image, for two reasons: +# 1. The cbfs master header pointer resides there +# 2. Ssme cbfs implementations assume that an image that resides below 4GB has +# a bootblock and get confused when the end of the image is at 4GB == 0. +MIN_BOOTBLOCK_SIZE = 4 + +# Files start aligned to this boundary in the CBFS +ENTRY_ALIGN = 0x40 + +# CBFSs must declare an architecture since much of the logic is designed with +# x86 in mind. The effect of setting this value is not well documented, but in +# general x86 is used and this makes use of a boot block and an image that ends +# at the end of 32-bit address space. +ARCHITECTURE_UNKNOWN = 0xffffffff +ARCHITECTURE_X86 = 0x00000001 +ARCHITECTURE_ARM = 0x00000010 +ARCHITECTURE_AARCH64 = 0x0000aa64 +ARCHITECTURE_MIPS = 0x00000100 +ARCHITECTURE_RISCV = 0xc001d0de +ARCHITECTURE_PPC64 = 0x407570ff + +ARCH_NAMES = { + ARCHITECTURE_UNKNOWN : 'unknown', + ARCHITECTURE_X86 : 'x86', + ARCHITECTURE_ARM : 'arm', + ARCHITECTURE_AARCH64 : 'arm64', + ARCHITECTURE_MIPS : 'mips', + ARCHITECTURE_RISCV : 'riscv', + ARCHITECTURE_PPC64 : 'ppc64', + } + +# File types. Only supported ones are included here +TYPE_CBFSHEADER = 0x02 # Master header, HEADER_FORMAT +TYPE_STAGE = 0x10 # Stage, holding an executable, see STAGE_FORMAT +TYPE_RAW = 0x50 # Raw file, possibly compressed +TYPE_EMPTY = 0xffffffff # Empty data + +# Compression types +COMPRESS_NONE, COMPRESS_LZMA, COMPRESS_LZ4 = range(3) + +COMPRESS_NAMES = { + COMPRESS_NONE : 'none', + COMPRESS_LZMA : 'lzma', + COMPRESS_LZ4 : 'lz4', + } + +def find_arch(find_name): + """Look up an architecture name + + Args: + find_name: Architecture name to find + + Returns: + ARCHITECTURE_... value or None if not found + """ + for arch, name in ARCH_NAMES.items(): + if name == find_name: + return arch + return None + +def find_compress(find_name): + """Look up a compression algorithm name + + Args: + find_name: Compression algorithm name to find + + Returns: + COMPRESS_... value or None if not found + """ + for compress, name in COMPRESS_NAMES.items(): + if name == find_name: + return compress + return None + +def compress_name(compress): + """Look up the name of a compression algorithm + + Args: + compress: Compression algorithm number to find (COMPRESS_...) + + Returns: + Compression algorithm name (string) + + Raises: + KeyError if the algorithm number is invalid + """ + return COMPRESS_NAMES[compress] + +def align_int(val, align): + """Align a value up to the given alignment + + Args: + val: Integer value to align + align: Integer alignment value (e.g. 4 to align to 4-byte boundary) + + Returns: + integer value aligned to the required boundary, rounding up if necessary + """ + return int((val + align - 1) / align) * align + +def align_int_down(val, align): + """Align a value down to the given alignment + + Args: + val: Integer value to align + align: Integer alignment value (e.g. 4 to align to 4-byte boundary) + + Returns: + integer value aligned to the required boundary, rounding down if + necessary + """ + return int(val / align) * align + +def _pack_string(instr): + """Pack a string to the required aligned size by adding padding + + Args: + instr: String to process + + Returns: + String with required padding (at least one 0x00 byte) at the end + """ + val = tools.ToBytes(instr) + pad_len = align_int(len(val) + 1, FILENAME_ALIGN) + return val + tools.GetBytes(0, pad_len - len(val)) + + +class CbfsFile(object): + """Class to represent a single CBFS file + + This is used to hold the information about a file, including its contents. + Use the get_data_and_offset() method to obtain the raw output for writing to + CBFS. + + Properties: + name: Name of file + offset: Offset of file data from start of file header + cbfs_offset: Offset of file data in bytes from start of CBFS, or None to + place this file anyway + data: Contents of file, uncompressed + data_len: Length of (possibly compressed) data in bytes + ftype: File type (TYPE_...) + compression: Compression type (COMPRESS_...) + memlen: Length of data in memory, i.e. the uncompressed length, None if + no compression algortihm is selected + load: Load address in memory if known, else None + entry: Entry address in memory if known, else None. This is where + execution starts after the file is loaded + base_address: Base address to use for 'stage' files + erase_byte: Erase byte to use for padding between the file header and + contents (used for empty files) + size: Size of the file in bytes (used for empty files) + """ + def __init__(self, name, ftype, data, cbfs_offset, compress=COMPRESS_NONE): + self.name = name + self.offset = None + self.cbfs_offset = cbfs_offset + self.data = data + self.ftype = ftype + self.compress = compress + self.memlen = None + self.load = None + self.entry = None + self.base_address = None + self.data_len = len(data) + self.erase_byte = None + self.size = None + + def decompress(self): + """Handle decompressing data if necessary""" + indata = self.data + if self.compress == COMPRESS_LZ4: + data = tools.Decompress(indata, 'lz4') + elif self.compress == COMPRESS_LZMA: + data = tools.Decompress(indata, 'lzma') + else: + data = indata + self.memlen = len(data) + self.data = data + self.data_len = len(indata) + + @classmethod + def stage(cls, base_address, name, data, cbfs_offset): + """Create a new stage file + + Args: + base_address: Int base address for memory-mapping of ELF file + name: String file name to put in CBFS (does not need to correspond + to the name that the file originally came from) + data: Contents of file + cbfs_offset: Offset of file data in bytes from start of CBFS, or + None to place this file anyway + + Returns: + CbfsFile object containing the file information + """ + cfile = CbfsFile(name, TYPE_STAGE, data, cbfs_offset) + cfile.base_address = base_address + return cfile + + @classmethod + def raw(cls, name, data, cbfs_offset, compress): + """Create a new raw file + + Args: + name: String file name to put in CBFS (does not need to correspond + to the name that the file originally came from) + data: Contents of file + cbfs_offset: Offset of file data in bytes from start of CBFS, or + None to place this file anyway + compress: Compression algorithm to use (COMPRESS_...) + + Returns: + CbfsFile object containing the file information + """ + return CbfsFile(name, TYPE_RAW, data, cbfs_offset, compress) + + @classmethod + def empty(cls, space_to_use, erase_byte): + """Create a new empty file of a given size + + Args: + space_to_use:: Size of available space, which must be at least as + large as the alignment size for this CBFS + erase_byte: Byte to use for contents of file (repeated through the + whole file) + + Returns: + CbfsFile object containing the file information + """ + cfile = CbfsFile('', TYPE_EMPTY, b'', None) + cfile.size = space_to_use - FILE_HEADER_LEN - FILENAME_ALIGN + cfile.erase_byte = erase_byte + return cfile + + def calc_start_offset(self): + """Check if this file needs to start at a particular offset in CBFS + + Returns: + None if the file can be placed anywhere, or + the largest offset where the file could start (integer) + """ + if self.cbfs_offset is None: + return None + return self.cbfs_offset - self.get_header_len() + + def get_header_len(self): + """Get the length of headers required for a file + + This is the minimum length required before the actual data for this file + could start. It might start later if there is padding. + + Returns: + Total length of all non-data fields, in bytes + """ + name = _pack_string(self.name) + hdr_len = len(name) + FILE_HEADER_LEN + if self.ftype == TYPE_STAGE: + pass + elif self.ftype == TYPE_RAW: + hdr_len += ATTR_COMPRESSION_LEN + elif self.ftype == TYPE_EMPTY: + pass + else: + raise ValueError('Unknown file type %#x\n' % self.ftype) + return hdr_len + + def get_data_and_offset(self, offset=None, pad_byte=None): + """Obtain the contents of the file, in CBFS format and the offset of + the data within the file + + Returns: + tuple: + bytes representing the contents of this file, packed and aligned + for directly inserting into the final CBFS output + offset to the file data from the start of the returned data. + """ + name = _pack_string(self.name) + hdr_len = len(name) + FILE_HEADER_LEN + attr_pos = 0 + content = b'' + attr = b'' + pad = b'' + data = self.data + if self.ftype == TYPE_STAGE: + elf_data = elf.DecodeElf(data, self.base_address) + content = struct.pack(STAGE_FORMAT, self.compress, + elf_data.entry, elf_data.load, + len(elf_data.data), elf_data.memsize) + data = elf_data.data + elif self.ftype == TYPE_RAW: + orig_data = data + if self.compress == COMPRESS_LZ4: + data = tools.Compress(orig_data, 'lz4') + elif self.compress == COMPRESS_LZMA: + data = tools.Compress(orig_data, 'lzma') + self.memlen = len(orig_data) + self.data_len = len(data) + attr = struct.pack(ATTR_COMPRESSION_FORMAT, + FILE_ATTR_TAG_COMPRESSION, ATTR_COMPRESSION_LEN, + self.compress, self.memlen) + elif self.ftype == TYPE_EMPTY: + data = tools.GetBytes(self.erase_byte, self.size) + else: + raise ValueError('Unknown type %#x when writing\n' % self.ftype) + if attr: + attr_pos = hdr_len + hdr_len += len(attr) + if self.cbfs_offset is not None: + pad_len = self.cbfs_offset - offset - hdr_len + if pad_len < 0: # pragma: no cover + # Test coverage of this is not available since this should never + # happen. It indicates that get_header_len() provided an + # incorrect value (too small) so that we decided that we could + # put this file at the requested place, but in fact a previous + # file extends far enough into the CBFS that this is not + # possible. + raise ValueError("Internal error: CBFS file '%s': Requested offset %#x but current output position is %#x" % + (self.name, self.cbfs_offset, offset)) + pad = tools.GetBytes(pad_byte, pad_len) + hdr_len += pad_len + + # This is the offset of the start of the file's data, + size = len(content) + len(data) + hdr = struct.pack(FILE_HEADER_FORMAT, FILE_MAGIC, size, + self.ftype, attr_pos, hdr_len) + + # Do a sanity check of the get_header_len() function, to ensure that it + # stays in lockstep with this function + expected_len = self.get_header_len() + actual_len = len(hdr + name + attr) + if expected_len != actual_len: # pragma: no cover + # Test coverage of this is not available since this should never + # happen. It probably indicates that get_header_len() is broken. + raise ValueError("Internal error: CBFS file '%s': Expected headers of %#x bytes, got %#d" % + (self.name, expected_len, actual_len)) + return hdr + name + attr + pad + content + data, hdr_len + + +class CbfsWriter(object): + """Class to handle writing a Coreboot File System (CBFS) + + Usage is something like: + + cbw = CbfsWriter(size) + cbw.add_file_raw('u-boot', tools.ReadFile('u-boot.bin')) + ... + data, cbfs_offset = cbw.get_data_and_offset() + + Attributes: + _master_name: Name of the file containing the master header + _size: Size of the filesystem, in bytes + _files: Ordered list of files in the CBFS, each a CbfsFile + _arch: Architecture of the CBFS (ARCHITECTURE_...) + _bootblock_size: Size of the bootblock, typically at the end of the CBFS + _erase_byte: Byte to use for empty space in the CBFS + _align: Alignment to use for files, typically ENTRY_ALIGN + _base_address: Boot block offset in bytes from the start of CBFS. + Typically this is located at top of the CBFS. It is 0 when there is + no boot block + _header_offset: Offset of master header in bytes from start of CBFS + _contents_offset: Offset of first file header + _hdr_at_start: True if the master header is at the start of the CBFS, + instead of the end as normal for x86 + _add_fileheader: True to add a fileheader around the master header + """ + def __init__(self, size, arch=ARCHITECTURE_X86): + """Set up a new CBFS + + This sets up all properties to default values. Files can be added using + add_file_raw(), etc. + + Args: + size: Size of CBFS in bytes + arch: Architecture to declare for CBFS + """ + self._master_name = 'cbfs master header' + self._size = size + self._files = OrderedDict() + self._arch = arch + self._bootblock_size = 0 + self._erase_byte = 0xff + self._align = ENTRY_ALIGN + self._add_fileheader = False + if self._arch == ARCHITECTURE_X86: + # Allow 4 bytes for the header pointer. That holds the + # twos-compliment negative offset of the master header in bytes + # measured from one byte past the end of the CBFS + self._base_address = self._size - max(self._bootblock_size, + MIN_BOOTBLOCK_SIZE) + self._header_offset = self._base_address - HEADER_LEN + self._contents_offset = 0 + self._hdr_at_start = False + else: + # For non-x86, different rules apply + self._base_address = 0 + self._header_offset = align_int(self._base_address + + self._bootblock_size, 4) + self._contents_offset = align_int(self._header_offset + + FILE_HEADER_LEN + + self._bootblock_size, self._align) + self._hdr_at_start = True + + def _skip_to(self, fd, offset): + """Write out pad bytes until a given offset + + Args: + fd: File objext to write to + offset: Offset to write to + """ + if fd.tell() > offset: + raise ValueError('No space for data before offset %#x (current offset %#x)' % + (offset, fd.tell())) + fd.write(tools.GetBytes(self._erase_byte, offset - fd.tell())) + + def _pad_to(self, fd, offset): + """Write out pad bytes and/or an empty file until a given offset + + Args: + fd: File objext to write to + offset: Offset to write to + """ + self._align_to(fd, self._align) + upto = fd.tell() + if upto > offset: + raise ValueError('No space for data before pad offset %#x (current offset %#x)' % + (offset, upto)) + todo = align_int_down(offset - upto, self._align) + if todo: + cbf = CbfsFile.empty(todo, self._erase_byte) + fd.write(cbf.get_data_and_offset()[0]) + self._skip_to(fd, offset) + + def _align_to(self, fd, align): + """Write out pad bytes until a given alignment is reached + + This only aligns if the resulting output would not reach the end of the + CBFS, since we want to leave the last 4 bytes for the master-header + pointer. + + Args: + fd: File objext to write to + align: Alignment to require (e.g. 4 means pad to next 4-byte + boundary) + """ + offset = align_int(fd.tell(), align) + if offset < self._size: + self._skip_to(fd, offset) + + def add_file_stage(self, name, data, cbfs_offset=None): + """Add a new stage file to the CBFS + + Args: + name: String file name to put in CBFS (does not need to correspond + to the name that the file originally came from) + data: Contents of file + cbfs_offset: Offset of this file's data within the CBFS, in bytes, + or None to place this file anywhere + + Returns: + CbfsFile object created + """ + cfile = CbfsFile.stage(self._base_address, name, data, cbfs_offset) + self._files[name] = cfile + return cfile + + def add_file_raw(self, name, data, cbfs_offset=None, + compress=COMPRESS_NONE): + """Create a new raw file + + Args: + name: String file name to put in CBFS (does not need to correspond + to the name that the file originally came from) + data: Contents of file + cbfs_offset: Offset of this file's data within the CBFS, in bytes, + or None to place this file anywhere + compress: Compression algorithm to use (COMPRESS_...) + + Returns: + CbfsFile object created + """ + cfile = CbfsFile.raw(name, data, cbfs_offset, compress) + self._files[name] = cfile + return cfile + + def _write_header(self, fd, add_fileheader): + """Write out the master header to a CBFS + + Args: + fd: File object + add_fileheader: True to place the master header in a file header + record + """ + if fd.tell() > self._header_offset: + raise ValueError('No space for header at offset %#x (current offset %#x)' % + (self._header_offset, fd.tell())) + if not add_fileheader: + self._pad_to(fd, self._header_offset) + hdr = struct.pack(HEADER_FORMAT, HEADER_MAGIC, HEADER_VERSION2, + self._size, self._bootblock_size, self._align, + self._contents_offset, self._arch, 0xffffffff) + if add_fileheader: + name = _pack_string(self._master_name) + fd.write(struct.pack(FILE_HEADER_FORMAT, FILE_MAGIC, len(hdr), + TYPE_CBFSHEADER, 0, + FILE_HEADER_LEN + len(name))) + fd.write(name) + self._header_offset = fd.tell() + fd.write(hdr) + self._align_to(fd, self._align) + else: + fd.write(hdr) + + def get_data(self): + """Obtain the full contents of the CBFS + + Thhis builds the CBFS with headers and all required files. + + Returns: + 'bytes' type containing the data + """ + fd = io.BytesIO() + + # THe header can go at the start in some cases + if self._hdr_at_start: + self._write_header(fd, add_fileheader=self._add_fileheader) + self._skip_to(fd, self._contents_offset) + + # Write out each file + for cbf in self._files.values(): + # Place the file at its requested place, if any + offset = cbf.calc_start_offset() + if offset is not None: + self._pad_to(fd, align_int_down(offset, self._align)) + pos = fd.tell() + data, data_offset = cbf.get_data_and_offset(pos, self._erase_byte) + fd.write(data) + self._align_to(fd, self._align) + cbf.calced_cbfs_offset = pos + data_offset + if not self._hdr_at_start: + self._write_header(fd, add_fileheader=self._add_fileheader) + + # Pad to the end and write a pointer to the CBFS master header + self._pad_to(fd, self._base_address or self._size - 4) + rel_offset = self._header_offset - self._size + fd.write(struct.pack('<I', rel_offset & 0xffffffff)) + + return fd.getvalue() + + +class CbfsReader(object): + """Class to handle reading a Coreboot File System (CBFS) + + Usage is something like: + cbfs = cbfs_util.CbfsReader(data) + cfile = cbfs.files['u-boot'] + self.WriteFile('u-boot.bin', cfile.data) + + Attributes: + files: Ordered list of CbfsFile objects + align: Alignment to use for files, typically ENTRT_ALIGN + stage_base_address: Base address to use when mapping ELF files into the + CBFS for TYPE_STAGE files. If this is larger than the code address + of the ELF file, then data at the start of the ELF file will not + appear in the CBFS. Currently there are no tests for behaviour as + documentation is sparse + magic: Integer magic number from master header (HEADER_MAGIC) + version: Version number of CBFS (HEADER_VERSION2) + rom_size: Size of CBFS + boot_block_size: Size of boot block + cbfs_offset: Offset of the first file in bytes from start of CBFS + arch: Architecture of CBFS file (ARCHITECTURE_...) + """ + def __init__(self, data, read=True): + self.align = ENTRY_ALIGN + self.arch = None + self.boot_block_size = None + self.cbfs_offset = None + self.files = OrderedDict() + self.magic = None + self.rom_size = None + self.stage_base_address = 0 + self.version = None + self.data = data + if read: + self.read() + + def read(self): + """Read all the files in the CBFS and add them to self.files""" + with io.BytesIO(self.data) as fd: + # First, get the master header + if not self._find_and_read_header(fd, len(self.data)): + raise ValueError('Cannot find master header') + fd.seek(self.cbfs_offset) + + # Now read in the files one at a time + while True: + cfile = self._read_next_file(fd) + if cfile: + self.files[cfile.name] = cfile + elif cfile is False: + break + + def _find_and_read_header(self, fd, size): + """Find and read the master header in the CBFS + + This looks at the pointer word at the very end of the CBFS. This is an + offset to the header relative to the size of the CBFS, which is assumed + to be known. Note that the offset is in *little endian* format. + + Args: + fd: File to read from + size: Size of file + + Returns: + True if header was found, False if not + """ + orig_pos = fd.tell() + fd.seek(size - 4) + rel_offset, = struct.unpack('<I', fd.read(4)) + pos = (size + rel_offset) & 0xffffffff + fd.seek(pos) + found = self._read_header(fd) + if not found: + print('Relative offset seems wrong, scanning whole image') + for pos in range(0, size - HEADER_LEN, 4): + fd.seek(pos) + found = self._read_header(fd) + if found: + break + fd.seek(orig_pos) + return found + + def _read_next_file(self, fd): + """Read the next file from a CBFS + + Args: + fd: File to read from + + Returns: + CbfsFile object, if found + None if no object found, but data was parsed (e.g. TYPE_CBFSHEADER) + False if at end of CBFS and reading should stop + """ + file_pos = fd.tell() + data = fd.read(FILE_HEADER_LEN) + if len(data) < FILE_HEADER_LEN: + print('File header at %x ran out of data' % file_pos) + return False + magic, size, ftype, attr, offset = struct.unpack(FILE_HEADER_FORMAT, + data) + if magic != FILE_MAGIC: + return False + pos = fd.tell() + name = self._read_string(fd) + if name is None: + print('String at %x ran out of data' % pos) + return False + + if DEBUG: + print('name', name) + + # If there are attribute headers present, read those + compress = self._read_attr(fd, file_pos, attr, offset) + if compress is None: + return False + + # Create the correct CbfsFile object depending on the type + cfile = None + cbfs_offset = file_pos + offset + fd.seek(cbfs_offset, io.SEEK_SET) + if ftype == TYPE_CBFSHEADER: + self._read_header(fd) + elif ftype == TYPE_STAGE: + data = fd.read(STAGE_LEN) + cfile = CbfsFile.stage(self.stage_base_address, name, b'', + cbfs_offset) + (cfile.compress, cfile.entry, cfile.load, cfile.data_len, + cfile.memlen) = struct.unpack(STAGE_FORMAT, data) + cfile.data = fd.read(cfile.data_len) + elif ftype == TYPE_RAW: + data = fd.read(size) + cfile = CbfsFile.raw(name, data, cbfs_offset, compress) + cfile.decompress() + if DEBUG: + print('data', data) + elif ftype == TYPE_EMPTY: + # Just read the data and discard it, since it is only padding + fd.read(size) + cfile = CbfsFile('', TYPE_EMPTY, b'', cbfs_offset) + else: + raise ValueError('Unknown type %#x when reading\n' % ftype) + if cfile: + cfile.offset = offset + + # Move past the padding to the start of a possible next file. If we are + # already at an alignment boundary, then there is no padding. + pad = (self.align - fd.tell() % self.align) % self.align + fd.seek(pad, io.SEEK_CUR) + return cfile + + @classmethod + def _read_attr(cls, fd, file_pos, attr, offset): + """Read attributes from the file + + CBFS files can have attributes which are things that cannot fit into the + header. The only attributes currently supported are compression and the + unused tag. + + Args: + fd: File to read from + file_pos: Position of file in fd + attr: Offset of attributes, 0 if none + offset: Offset of file data (used to indicate the end of the + attributes) + + Returns: + Compression to use for the file (COMPRESS_...) + """ + compress = COMPRESS_NONE + if not attr: + return compress + attr_size = offset - attr + fd.seek(file_pos + attr, io.SEEK_SET) + while attr_size: + pos = fd.tell() + hdr = fd.read(8) + if len(hdr) < 8: + print('Attribute tag at %x ran out of data' % pos) + return None + atag, alen = struct.unpack(">II", hdr) + data = hdr + fd.read(alen - 8) + if atag == FILE_ATTR_TAG_COMPRESSION: + # We don't currently use this information + atag, alen, compress, _decomp_size = struct.unpack( + ATTR_COMPRESSION_FORMAT, data) + elif atag == FILE_ATTR_TAG_UNUSED2: + break + else: + print('Unknown attribute tag %x' % atag) + attr_size -= len(data) + return compress + + def _read_header(self, fd): + """Read the master header + + Reads the header and stores the information obtained into the member + variables. + + Args: + fd: File to read from + + Returns: + True if header was read OK, False if it is truncated or has the + wrong magic or version + """ + pos = fd.tell() + data = fd.read(HEADER_LEN) + if len(data) < HEADER_LEN: + print('Header at %x ran out of data' % pos) + return False + (self.magic, self.version, self.rom_size, self.boot_block_size, + self.align, self.cbfs_offset, self.arch, _) = struct.unpack( + HEADER_FORMAT, data) + return self.magic == HEADER_MAGIC and ( + self.version == HEADER_VERSION1 or + self.version == HEADER_VERSION2) + + @classmethod + def _read_string(cls, fd): + """Read a string from a file + + This reads a string and aligns the data to the next alignment boundary + + Args: + fd: File to read from + + Returns: + string read ('str' type) encoded to UTF-8, or None if we ran out of + data + """ + val = b'' + while True: + data = fd.read(FILENAME_ALIGN) + if len(data) < FILENAME_ALIGN: + return None + pos = data.find(b'\0') + if pos == -1: + val += data + else: + val += data[:pos] + break + return val.decode('utf-8') + + +def cbfstool(fname, *cbfs_args, **kwargs): + """Run cbfstool with provided arguments + + If the tool fails then this function raises an exception and prints out the + output and stderr. + + Args: + fname: Filename of CBFS + *cbfs_args: List of arguments to pass to cbfstool + + Returns: + CommandResult object containing the results + """ + args = ['cbfstool', fname] + list(cbfs_args) + if kwargs.get('base') is not None: + args += ['-b', '%#x' % kwargs['base']] + result = command.RunPipe([args], capture=not VERBOSE, + capture_stderr=not VERBOSE, raise_on_error=False) + if result.return_code: + print(result.stderr, file=sys.stderr) + raise Exception("Failed to run (error %d): '%s'" % + (result.return_code, ' '.join(args))) |